Plural electron gun assembly and magnetic convergence cage



Aug. 23, 1966 R. H. HUGHES 3,268,753

PLURAL ELECTRON GUN ASSEMBLY AND MAGNETIC CONVERGENCE CAGE Original Filed July 6, 1962 2 Sheets-Sheet 1 INVENTOR.

K/c/mw HUGHZS J/Z am;

Aug. 23, 1966 R. H. HUGHES PLURAL ELECTRON GUN ASSEMBLY AND MAGNETIC CONVERGENCE CAGE 2 Sheets- Sheet 2 Original Filed July 6, 1962 United States Patent Office 3,253,753 Patented August 23, 1966 9 Claims. Cl. 313-69) This is a division of my application, Serial No. 208,- 017, filed July 6, 1962, assigned to the same assignee.

This invention relates to cathode ray tubes and to electron guns therefor. The invention is particularly directed to cathode ray tubes having a unitary assembly comprising a plurality of electron guns disposed side-by-side for projecting and converging a plurality of electron beams onto a luminescent screen. Such electron gun assemblies are, for example, used in direct view color cathode ray picture tubes of the shadow mask type for home television use.

It is an object of this invention to provide new and improved means such as a plural electron gun assembly of the type described for generating a plurality of electron beams.

Another object of the invention is the provision of a plural gun assembly which includes new and improved structure for effecting both lateral and radial electron beam convergence.

Features of this invention may, for example, be embodied in a plural electron gun assembly wherein each of the electron guns includes, in the order named, axially aligned cathode, control grid, screen grid, focus, and anode electrodes which are mounted in fixed relationship along a plurality of elongated insulator support rods. In a preferred embodiment of the invention, the plural gun assembly includes three similar guns disposed in delta array symmetrically about the central longitudinal axis of the cathode ray tube. Electrodes of the three guns are mounted on three glass support rods, each of which is disposed alongside a different two of the three guns. Each electrode is supported by members extending therefrom which are fixed to two of the support rods. A dynamic convergence cage, mounted on the anodes, includes a plurality of pairs of plate-like pole pieces, each pair of which straddles the beam path of one of the electron guns.

According to one feature of the invention, in a delta arrayed three-gun assembly, one set of corresponding electrodes (e.g., the three focus electrodes) are mounted on three magnetic support straps which also serve as magnet pole pieces in a lateral beam convergence arrangement. The straps are disposed in a somewhat triangular array with their ends fixed to a plurality of insulator support rods. Each of the focus electrodes is attached to one of the straps between the ends thereof and is disposed outside the triangular array thereof. A pair of cooperating magnet means externally of the cathode ray tube envelope are disposed adjacent to two of the apexes of the triangular array of straps.

According to another feature of the invention the dynamic convergence cage com-prises a cup whose cylindrical wall is longitudinally slotted at spaced circumferential locations. The plate-like pole pieces thereof are disposed through the slots and each includes a flange which lies along the outer cylindrical surface of the cup. The flange has edge portions which lie flush with, and are welded to, the outer cylindrical surface of the cup, and a central raised portion between the edge portions which is spaced close to the cathode ray tube envelope, and hence, to external magnet means.

The various features may be employed singly or in combination.

In the drawings:

FIG. 1 is a partial longitudinal section view with parts broken away of a cathode ray tube embodying the invention;

FIG. 2 is an enlarged perspective view of the combination beading strap and lateral convergence pole piece of the electron gun assembly of FIG. 1;

FIG. 3 is an enlarged transverse section of the electron gun and lateral convergence assemblies of FIG. 1 taken along line 3-3 thereof;

FIG. 4 is an enlarged section view of the electron gun and dynamic convergence assemblies of FIG. 1 taken along line 44 thereof; and,

FIG. 5 is an enlarged section of a portion of the convergence cage assembly of FIG. 4 taken along line 5-5 thereof.

In FIG. 1, by way of example, the invention is shown as embodied in a direct view color cathode ray picture tube 10 of the shadow mask type. The tube 10 comprises an envelope which includes a neck 12, a funnel 13, a faceplate 14, and a stem structure 15. A plurality of lead-in pins 16, over which an indexing wafer base 17 is disposed, are sealed through the stem 15. A mosaic dot phosphor screen 18, which may be aluminized according to known practices, is disposed on the inner surface of the faceplate 14. An apertured shadow mask 20 having an array of apertures therethnough, which is related to the array of phosphor dots of the mosaic screen 18, is mounted adjacent to the screen. Means in the form of a unitary electron gun assembly 22 comprising three substantially identical electron guns is disposed in the neck 12 and adapted to project three separate electron beams through a beam deflection zone 24 toward the mosaic screen 18. A magnetic deflection yoke 25 is provided for establishing beam deflection fields in the deflection zone 24. As shown, for example, in FIGS. 3 and 4, the electron guns of the assembly 22 are disposed symmetrically about the central longitudinal axis of the tube 10 in an equilateral triangular (delta) array. In FIG. 1 only two of the three guns are shown.

Each of the three guns comprises a cathode assembly 26, a control grid 27, a screen grid 28, a focus electrode 29, and an anode 30, all of which are mounted in axially aligned spaced relationship along three insulator, e.g., glass, support rods 32. As shown in FIG. 3, each of the insulator rods 32 are disposed along side a different two of the three electron guns outwardly therefrom. Only one of these rods is shown in FIG. 1. The focus electrodes 29 are supported from the rods 32 by combination support straps and lateral convergence pole pieces 34 as hereinafter described with reference to FIGS. 2 and 3. The anodes are supported from the rods 32 by nonmagnetic straps 35 similar in shape to the pole piece straps 34. The cathode assembly 26, control electrode 27, and screen grid electrode 28 are supported from the rods 32 by integral strap-like tabs 42.

Heater filaments 48 for the cathodes are supported by a sectioned ring-shaped strap mounted on the insulator support rods 32.

A dynamic electron beam convergence cage 44 is mounted on the anodes 30 and cooperates with external magnet means 46 to maintain convergence of the three electron beams at all times during their scanning of a raster on the luminescent screen 13. The construction and operation of the dynamic convergence arrangement is hereinafter more fully described with reference to FIGS. 4 and 5.

The lead-in conductors 16 are connected by connections (not shown) to the filaments 48, the cathode assemblies 26, the control electrodes 27, the screen grid electrodes 28, and the focus electrodes 29 of the electron guns. An electrical conductive coating 52 on the inner wall of the funnel 13 extends from the luminescent screen 18 into the neck 12 where it makes contact with a plurality of spring bulb-spacing elements 54. An ultor potential applied to the coating 52 through a lead-in terminal in the funnel wall in the funnel 13, schematically illustrated by the arrow 56, is thus applied to the anodes 30, the convergence cage 34, and the luminescent screen 18.

FIGS. 2 and 3 illustrate the mounting of the focus electrodes 29 on the insulator support rods 32 and the novel lateral beam deflection convergence arrangement provided thereby. Each of the three focus electrodes 29 is mounted on a separate combination support strap and lateral convergence magnetic pole piece 34 made of magnetic material.

As shown in FIG. 2, the combination support straps and lateral convergence pole pieces 34 comprise a central arcuate electrode-receiving section 86 and two end sections 88. The end sections 88 are bent so as to extend in different directions at an angle of approximately 120 with each other. The end sections 88 are provided with E-shaped cutouts to produce a plurality of projections 90 which can be embedded in the insulator support rods 32.

As shown in FIG. 3, the three magnetic support-strappoles 34 are disposed in a somewhat triangular array with the ends of each strap being adjacent an end of a different strap and with these ends being embedded in the three insulator support rods 32. The three support-strappoles 34 are so disposed that the concave side of their arcuate electrode-receiving sections 86 face outwardly. The three tubular focus electrodes are thus mounted on the straps 34 on the outer facing sides thereof, that is, outside of the triangular array of the straps. Because the electrodes are disposed outside the triangular array of the straps 34, the straps serve to magnetically isolate the three electrodes 29 from each other.

As shown in FIG. 3, magnetic means 92 is provided externally of the neck 12 of the cathode ray tube for cooperation with the three support-strap-poles 34. The magnetic means 92 includes as its basic components, two bar magnets 94, which are disposed with like polarity poles substantially adjacent two of the apexes 95 of the triangular array of straps 34. Their opposite polarity poles are disposed radially outward therefrom. The bar magnets 94 may be either or both, permanently magnetized or electromagnetized by a pair of solenoids 96. The bar magnets 94 together with their solenoids 96 are retained in place by a magnetic strap 98 which is apertured near its ends to receive the bar magnets 94. The retaining strap 98 extends between the magnets 94 with at least a portion thereof disposed adjacent the tubular electrode 29 which is on the opposite side of the assembly 22 from the other apex 99 of the triangular array of straps 34. The retaining strap 98 is preferably contiguous with the neck 12. The retaining strap 98 is held on the neck 12 by a tension spring 100.

By virtue of the cooperative arrangement of the magnets 94 and the support strap poles 34, magnetic circuits are established as illustrated by the flux lines 102, 104 and 106. Flux created by the magnets 94 enter the ends of the straps 34 along paths 102. A portion of the flux is conducted by the upper strap toward the upper focus electrode 29 and then passes through space along the paths 104 to the retaining strap 98 through which it is conducted back to the magnets 94. The other portion of the flux is conducted by the lower straps 34 to the vicinity of the two lower focus electrodes 29 and thence pass through space along the paths 106 to the retaining strap 98 through which it is conducted back to the magnets 94. The direction of flux flow through the upper focus electrode is in a direction opposite to that through the two lower focus electrodes. Thus, the electron beam passing through the 4 upper focus electrode will be deflected in one lateral direction while the electron beams passing through the two lower focus electrodes will be deflected in the opposite lateral direction. By virtue of such opposite lateral deflections, maximum convergence sensitivity is obtained as described in US. Patent 2,847,598, issued on August 12, 1958, to R. H. Hughes.

In the event that the lateral convergence correction required is opposite that which would be provided by the magnet arrangement shown in FIG. 3, the magnets 94 can be reversed in the retaining strap 98. The flux flow and hence the lateral beam deflection will thus :be opposite that illustrated.

Although the magnets 94 are shown disposed exactly, radially outward from the apexes 95, they may instead be slightly shifted circumferentially around the neck 12 from the apexes so as to obtain a desired shaping of the magnetic fields within the tubular electrodes 29. Arrangements wherein the magnets 94 are described as disposed circumferentially adjacent the apexes 95 are meant to include arrangements in which the magnets 94 are so shifted.

The solenoids 96 may be energized either with a suitable time varying current or by direct current so that the lateral convergence may be either dynamically or statically provided.

FIGS. 4 and 5 illustrate the tube structure and external magnet means for providing dynamic radial convergence. Such convergence is known in the art and will therefore not be described in detail herein. A description of dynamic radial convergence may be found in the Hughes patent cited above and in US. Patent 2,752,520, issued on June 26, 1956, to A. M. Morrell.

As shown in FIGS. 4 and 5, the convergence cage 44 of tube 10 comprises a cup 110 having a cylindrical wall 112 and an end wall 114. A Y-shaped magnetic shield 115 divides the cup 110 into three equal parts. The end wall 114 is provided with three apertures 116, one in each of the three divisions of the cup 110, through which the electron beams from the three electron guns pass. The cylindrical wall 112 is provided with six longitudinal slots through which three pair of pole pieces 118 are disposed. Each pole piece 118 includes a plate-like element 119 and a flange 120. The plate-like elements 119 of each pair of pole pieces 118 are substantially parallel to each other and straddle the beam path of one of the electron guns. The flange 120 of each pole piece 118 lies along the external surface of the cylindrical wall 112. The flange 120 includes alternate flush and raised portions. The spaced-apart flush portions 122 and 124 are con tiguous with or lie flush with the cylindrical wall 112 and are welded thereto. The spaced-apart raised portions 126 and 128 are substantially parallel to but spaced from the cylindrical wall 112 and are disposed very close to the neck 12.

By virtue of this close spacing, maximum sensitivity of coupling between the pole piece 118 and the external mag-net 46 (is obtained. On the other hand, since the flush portions of the flange which are welded to the cylindnical Wall 112 are recessed from the neck 12, weld splash which might exist on the flange in the form of sharp peaks, is safely spaced from the conductive coating 52 on the neck 12. Were the coating 52 to be scnatched by weld splash peaks on the flange 120, portions of the coating might be scraped-off (and remain as harmful debris the finished cathode ray tube 10. The rflush and raised portions of the flange 120 tend to prevent such scrape-off.

One of the raised portions 128 extends beyond the axial extent of its associated plate-like element 119. Thus the coupling between the external magnet 46 and the pole piece 118 is not limited by the axial length of the. platelike element 119.

What is claimed is:

1. In an assembly for generating a plunality of separate electron beams, means including three tubular electrodes disposed in delta array with their axes substantially parallel and mounted on a plurality of insulator support rods, said three tubular electrodes being supported from three magnetic straps which are disposed in a generally triangulaiarray with their ends fixed in said insulator support rods, each of said tubular electrodes being disposed generally outside the triangular array of said straps and attached to a different one of said straps between the ends thereof.

2. In an assembly of three electron guns disposed sideby-side in delta array, each of said guns comprising a plurality of axially aligned electrodes including :a tubular electrode mounted in spaced relation along a plurality of insulator support rods disposed along side said guns generally outwardly of the delta array thereof, the improvement comprising three combination electrode support and magnet pole piece straps of magnetic material each of which comprises a central aminate-shaped, electrode receiving section and two end sections which extend irom said central arcuate section in different directions, said straps being disposed in a generally triangular array with the concave sides of their central arcnate sections iacing outwardly of the array thereof and with each end section of each strap being anchored in one of said insulator support rods, said tubular electrodes being attached to said straps on the outwardly iiacing concave surfaces of the arcuate electrode-receiving sections thereof.

3. In an assembly comprising three electron guns disposed sideby-side in delta array, each of said guns comprising a plurality of axially aligned electrodes including a tubular electrode mounted in spaced relation along a plurality of insulator support rods disposed along side said guns generally outwardly of the delta array thereof, the improvement comprising three combination electrode support and lateral convergence pole piece straps of magnetic material each of which comprises a central arcuateshaped, electrode-receiving section and two end sections which extend from said central :arcuate section at an angle of approximately 120 with each other, said straps being disposed in a generally triangular array with the concave sides of their central arcuate sections tacing outwardly of the array thereof and with each end section of each strap being disposed substantially parallel with the adjacent end section of another of said straps and anchored in one of said insulator support rods, said tubular electrodes being [attached to said straps on the outwardly flacing concave surfiaces of the arcuate electrode-receiving sections thereof.

4. The combination of a cathode ray tube including an electron gun assembly comprising three electron guns disposed side-by-side in a delta array, each of said guns comprising a plurality of electrodes including a tubular electrode mounted in spaced relation along a plurality of insulator support rods disposed along side said guns generally outwardly of the delta array thereof, three straps of magnetic material, each of which comprises a central arcuate electrode-receiving section and two end sections which extend from said central larcuate section in different directions, said straps being disposed in a generally triangular array with the concave sides of their central arcuate sections facing outwardly of the array thereof and with their end sections anchored in said insulator support rods, said tubular electrods being attached to said straps on the outer concave surfiaces of the 'arcuate electrode-receiving sections thereof, and magnet means comprising two magnets each of which is disposed with a pole thereof substantially adjacent ll-O a different one of two of the apexes of said triangular array of straps, and magnet retaining means of magnetic material attached to said magnets and extending therebetween with a portion thereof disposed adjacent to the one of said tubular electrodes which is on the opposite side of said electron gun assembly from the other apex of said triangular array of straps.

5. The combination of a cathode ray tube with magnet means external of said tube, said tube comprising an envelope including a neck section and an electron gun assembly comprising three substantially similar electron guns disposed side-by-side in a delta array within said neck section, each of said guns comprising a plurality of axially aligned electrodes including a tubular electrode mounted in spaced relation along three insulator support rods, each of which is disposed along side a different two of said guns generally outwardly of the delta array thereof, three combination electrode support and magnet pole piece straps of magnetic material, each of which comprises a central tarcuate electrode-receiving section and two end sections which extend firom said central arcuate section at an angle with each other, said straps being disposed in a generally triangular array with the concave sides of their central \arcuate sections facing outwardly of the array thereof \and with their end sections anchored in said insulator support rods, said tubular electrodes being attached to said straps on the outer concave surtaces of the arcuate electrode receiving section-s thereof, said magnet means comprising two bar magnets each of which is disposed with a pole thereof substantially adjacent to a different one of two of the apexes of said triangular array of straps, and a magnet retaining strap of magnetic material attached to said magnets and extending therebetween and disposed circumferentially along and adjacent to said neck section on the side of said electron gun assembly opposite the other apex of said triangular array of straps.

6. A magnetic convergence cage comprising a member having a cylindrical wall with a plurality of longitudinal slots therein, and a plurality of magnetic pole pieces each comprising a plate-like element disposed through one of said slots and a flange extending circumferentially along the outer surface of said cylindrical wall, said flange comprising a first portion which lies flush with said cylindrical wall and welded thereto and a second portion which is generally parallel to and spaced trom said cylindrical wall.

7. Means tor generating a plurality of electron beams along separate beam paths, said means including a magnetic convergence cage comprising a cylindrical cup having a plurality of longitudinal slots in the cylindrical wall thereof and a plurality of apertures in the end wall thereof disposed respectively coaxially with said electron beam paths, a plurality of pairs of magnetic pole pieces, each pole piece comprising a plate-like element with a [flange extending therefrom, the plate-like elements of each of said pole pieces extending through one of said slots into said cup substantially parallel to the plate-like element of the other pole piece of the same pair with each pair of plate-like elements straddling a different one of said beam paths, said flange being disposed circumferentially along the outer surfiace of the cylindrical wall of said cup, said fllange comprising spaced flush portions which lie flush with said cylindrical wall and are welded thereto and a raised portion between said iiush portions which is generally parallel to and spaced from said cylindrical wall.

8. An assembly comprising a plurality of electron guns disposed side-by-side with each of said guns including a plurality of axially aligned electrodes and a magnetic convergence cage mounted on the ends of said guns, said cage comprising a cylindrical cup having a plurality of longitudinal slots in the cylindrical wall thereof and la plunality of apertures in the end wall thereof disposed respectively coaxially with the electron beam paths of said electron guns, a plurality of parallel pairs of plate-like magnetic pole piece elements extending through said slots into said cup with a separate pair of said pole piece elernents straddling a different one of said beam paths, each of said plate-like pole piece elements having a flange extending circumferentially along the outer surfiace of the cylindrical wall of said :cup, said flange comprising a plurality of alternate flush and raised portions, said flush portions being contiguous with and welded to said icy-lind-nioal Wall land said raised ponti'ons being panallel to and spaced from cylindrical wall, one of said raise-d portions extending longitudinally along said cup beyond [the longitudinal slot in which its plate-like pole piece element is disposed.

9. In an assembly for generating a plurality of sepa rate electron beams, means including three tubular electrodes disposed in delta array with their axes substantially parallel and mounted on a plurality of insulator support rods, said three tubular electrodes being supported from three straps which are disposed in a generally triangular array with their ends fixed in said insulator support rods, each of said tubular electrodes being disposed generally outside the triangular array of said straps and attached to a different one of said straps between the ends thereof, at least one of said straps being magnetic.

References Cited by the Examiner UNITED STATES PATENTS 2,752,520 6/1956 Morrell 31370 2,849,646 8/ 1958 N oskowi cz 315- 13 3,188,507 6/1965 Law et a1. 3 l332 JAMES W. LAWRENCE, Primary Examiner.'

R. SEGAL, Assistant Examiner. 

9. IN AN ASSEMBLY FOR GENERATING A PLURALITY OF SEPARATE ELECTRON BEAMS, MEANS INCLUDING THREE TUBULAR ELECTRODES DISPOSED IN DELTA ARRAY WITH THEIR AXES SUBSTANTIALLY PARALLEL AND MOUNTED ON A PLURALITY OF INSULATOR SUPPORT RODS, SAID THREE TUBULAR ELECTRODES BEING SUPPORTED FROM THREE STRAPS WHICH ARE DISPOSED IN A GENERALLY TRIANGULAR ARRAY WITH THEIR ENDS FIXED IN SAID INSULATOR SUPPORT RODS, EACH OF SAID TUBULAR ELECTRODES BEING DISPOSED GENERALLY OUTSIDE THE TRIANGULAR ARRAY OF SAID STRAPS AND ATTACHED TO A DIFFERENT ONE OF SAID STRAPS BETWEEN THE ENDS THEREOF, AT LEAST ONE OF SAID STRAPS BEING MAGNETIC. 